This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Self-assembled nanostructures have been successfully exploited for a variety of purposes in medicine, materials science, and engineering. The proposed research centers on a particular kind of self-assembling molecule called peptide amphiphiles that form molecular hydrogels composed of nanofibers. These molecules have been utilized by our laboratory at Northwestern University to achieve a collection of bioengineering goals: as cell and tissue artificial scaffolds;as biomaterials that direct stem cell differentiation, cell migration, cellular response, and tissue regeneration after injury;and as vehicles for cell, peptide, nucleic acid, and protein delivery. Our experiments center on understanding supramolecular structures these molecules create by investigating molecular orientations and spatial distributions within the nanofiberous materials. The overall goal is to validate specific thermodynamic, kinetic, and molecular dynamic models of self-association and to uncover structure-function relationships of these engineered biomaterials. Future engineering of these specific molecules for biomedicine and therapeutics is contingent upon understanding all levels of the organizational behavior of these hydrogel systems. We believe that X-ray diffraction is an valuable addition to our present characterization methodologies by allowing molecular level resolution of this non-crystalline system. In particular, the use of synchrotron X-ray sources will provide the highest level of resolution of molecular packing in contrast to other traditional polymer characterization methodologies. Collaboration with fiber diffractionists currently making great strides in understanding other peptide/protein-based self-assembling systems will lead to effective translation of techniques, results, and broader impact to society across both fields.